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COMPLEX BRASSES

22Q

Iron Brasses

The addition of small quantities of iron imparts to brass properties
analogous to those of manganese brasses, and iron brasses have the same
applications as the latter. The analytical procedure is that indicated for
common brass (q.v.).

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* *

The iron brasses in more common use have the following mean compositions :
Sterro metal:  55-60% Cu, 38-42% Zn, 1-5-2% Fe, 0-0-8% Sn.
Aich's metal:  58-60% Cu, 36-41% Zn, 0-7-1-8% Fe, 0-1% Sn.

Aluminium Brasses

Aluminium brasses have properties similar to those of manganese and
iron brasses and find the same uses in naval construction. They are analysed
by the methods for complex brasses (#.&'.).

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* *

The aluminium brasses in more common use have the following mean per-
centage compositions (Guillet) :

(1)   Copper, 68-70;   zinc, 31-27;   aluminium, 3-1.

(2)        ,,        64-66 ;      ,,     33-30 ;            ,,         4-1.

(3)        „       58-6i ;      „     4°'5-37'5 ;      „          i-5~3-

COMPLEX   BRASSES

Complex brasses have properties very similar to those of manganese
brasses and are largely used, particularly for making propellers, anchors,
keels, torpedo tubes, etc.

; ' These brasses may contain at the same time: iron and manganese;
iron and aluminium ; iron, manganese, aluminium and, sometimes, tin.
Their analysis includes determinations of the components proper (Cu, Zn,
Mn, Fe, Al, Sn) and of any extraneous elements present as impurities (Pb,
P, S, Bi, etc.), and may be carried out electrolytically or by a combined
gravimetric and volumetric method.

A.   Electrolytic Method1

In a small covered beaker, I gram of the sample is dissolved in 10-12
c.c. of nitric acid (D 1-2) at a gentle heat.

1. Determination of the Tin.—The solution is diluted with 15-20
c.c. of water and, if turbid owing to the presence of metastannic acid,
evaporated to dryness, the residue being taken up with a few drops of nitric
acid and a little water. The liquid is heated for some time and the meta-
stannic acid filtered off, washed with hot water acidified with nitric acid,
ignited and weighed : Sn02 X 0-7881 = Sn.

1 Belasio and MarcMonnescbi:   Annali di Chimica appUcata, 1914, I, p. 127.one or more other elements (especially lead, tin,